The present invention relates to variable displacement compressors that are used in, for example, vehicle air conditioners and adjust the pressure in a crank chamber to vary displacement.
This type of compressor adds lubricant oil mist to refrigerant gas to lubricate the interior of the compressor. The lubricant oil may be isolated from the refrigerant gas that is discharged from the compressor to an external refrigerant circuit, as disclosed in Japanese Unexamined Patent Publication No. 10-281060. The oil is then recirculated to the interior of the compressor, thus further lubricating the interior of the compressor.
This structure includes an oil separator that is located between a discharge chamber and the external refrigerant circuit. An oil return passage connects a crank chamber to the oil separator. After the oil separator separates lubricant oil from refrigerant gas, the lubricant oil returns to the crank chamber through the oil return passage. The oil return passage functions also as a supply passage through which the pressure in the discharge chamber is introduced to the crank chamber, thus controlling the compressor displacement. The supply passage includes a control valve that changes its opening size to adjust the pressure in the crank chamber. A bleed passage connects the crank chamber to a suction chamber. The pressure in the crank chamber is introduced to the suction chamber through the bleed passage to control the displacement.
However, after having been discharged from the crank chamber, lubricant oil must flow in the bleed passage, the suction chamber, compression chambers, and the discharge chamber before reaching the oil separator. This prolongs the time required for recirculation of the lubricant oil to the crank chamber. Accordingly, a relatively small amount of lubricant oil is retained in the crank chamber.
Further, since the entire supply passage functions as the oil return passage, lubricant oil passes through the control valve when flowing from the oil separator to the crank chamber. Thus, the opening size of the control valve may affect the amount of the oil that flows from the oil separator to the crank chamber. That is, for example, if the control valve fully closes the supply passage, the oil flow from the oil separator to the crank chamber stops.
Accordingly, it is an objective of the present invention to provide a variable displacement compressor that rapidly recovers lubricant oil from a control chamber to return the oil to the control chamber.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the present invention is a variable displacement compressor for compressing refrigerant gas that contains lubricant. The compressor compresses the refrigerant gas supplied from a suction chamber to a compression chamber and sends the compressed refrigerant gas to a discharge chamber when a drive shaft rotates. The displacement of the compressor varies in accordance with the pressure in a control chamber located in a compressor housing. The compressor has a supply passage for supplying the refrigerant gas from the discharge chamber to the control chamber and a bleed passage for bleeding the refrigerant gas from the control chamber to the suction chamber. The compressor includes a separator, a lubricant chamber, and a return passage. The separator is located in the bleed passage and rotates together with the drive shaft, thus centrifugally separating the lubricant from the refrigerant gas that flows in the bleed passage. The lubricant chamber is formed in the housing and receives the separated lubricant. The pressure in the lubricant chamber is equal to or greater than the pressure in the control chamber. The return passage is formed in the housing and returns the lubricant from the lubricant chamber to the control chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.